Method for determining activation of ISR capability

ABSTRACT

One disclosure of the present specification provides a method for determining whether to activate an idle mode signaling reduction (ISR) capability in a network entity for managing mobility of user equipment. The method for determining whether to activate the ISR capability comprises the steps of: obtaining information related to a proximity service of the user equipment; receiving from the user equipment a location refresh request message; determining whether to activate the ISR based on ISR capability information of a network node that had been just previously in charge of the user equipment, ISR capability information of the network entity, and information related to the proximity service of the user equipment; and transmitting a location refresh acceptance message to the user equipment after the determination.

This application is a 35 USC §371 National Stage entry of InternationalApplication No. PCT/KR2014/004045 filed on May 7, 2014, and claimspriority to U.S. Provisional Application Nos. 61/820,187 filed on May 7,2013 and 61/820,186 filed on May 7, 2013, all of which are herebyincorporated by reference in their entireties as if fully set forthherein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a method of determining whether toactivate an idle mode signaling reduction (ISR) capability.

Related Art

In 3GPP in which technical standards for mobile communication systemsare established, in order to handle 4th generation communication andseveral related forums and new technologies, research on Long TermEvolution/System Architecture Evolution (LTE/SAE) technology has startedas part of efforts to optimize and improve the performance of 3GPPtechnologies from the end of the year 2004.

SAE that has been performed based on 3GPP SA WG2 is research regardingnetwork technology that aims to determine the structure of a network andto support mobility between heterogeneous networks in line with an LTEtask of a 3GPP TSG RAN and is one of recent important standardizationissues of 3GPP. SAE is a task for developing a 3GPP system into a systemthat supports various radio access technologies based on an IP, and thetask has been carried out for the purpose of an optimized packet-basedsystem which minimizes transmission delay with a more improved datatransmission capability.

An Evolved Packet System (EPS) higher level reference model defined in3GPP SA WG2 includes a non-roaming case and roaming cases having variousscenarios, and for details therefor, reference can be made to 3GPPstandard documents TS 23.401 and TS 23.402. A network configuration ofFIG. 1 has been briefly reconfigured from the EPS higher level referencemodel.

FIG. 1 shows the configuration of an evolved mobile communicationnetwork.

As illustrated, an evolved UMTS terrestrial radio access network(E-UTRAN) is connected to an evolved packet core (EPC). The E-UTRAN is aradio access network defined after 3GPP release-8, and is also called a4^(th) generation (4G) (i.e., LTE) network. A radio access networkbefore the LTE, i.e., a 3^(rd) generation (3G) radio access network, isa UTRAN.

The E-UTRAN includes a base station (BS) (or eNodeB) 20 which provides acontrol plane and a user plane to a user equipment (UE). The BSs (oreNodeBs) 20 may be interconnected by means of an X2 interface.

Layers of a radio interface protocol between the UE and the BS (oreNodeB) 20 can be classified into a first layer (L1), a second layer(L2), and a third layer (L3) based on the lower three layers of the opensystem interconnection (OSI) model that is well-known in thecommunication system. Among them, a physical (PHY) layer belonging tothe first layer provides an information transfer service by using aphysical channel, and a radio resource control (RRC) layer belonging tothe third layer serves to control a radio resource between the UE andthe network. For this, the RRC layer exchanges an RRC message betweenthe UE and the BS.

Meanwhile, the EPC may include various constitutional elements. Amongthem, a mobility management entity (MME) 51, a serving gateway (S-GW)52, a packet data network gateway (PDN GW) 53, and a home subscriberserver (HSS) 54 are illustrated in FIG. 1.

The BS (or eNodeB) 20 is connected to the MME 51 of the EPC through anS1 interface, and is connected to the S-GW 52 through S1-U.

The S-GW 52 is an element that operates at a boundary point between aRadio Access Network (RAN) and a core network and has a function ofmaintaining a data path between an eNodeB 22 and the PDN GW 53.Furthermore, if a terminal (or User Equipment (UE) moves in a region inwhich service is provided by the eNodeB 22, the S-GW 52 plays a role ofa local mobility anchor point. That is, for mobility within an E-UTRAN(i.e., a Universal Mobile Telecommunications System (Evolved-UMTS)Terrestrial Radio Access Network defined after 3GPP release-8), packetscan be routed through the S-GW 52. Furthermore, the S-GW 52 may play arole of an anchor point for mobility with another 3GPP network (i.e., aRAN defined prior to 3GPP release-8, for example, a UTRAN or GlobalSystem for Mobile communication (GSM) (GERAN)/Enhanced Data rates forGlobal Evolution (EDGE) Radio Access Network).

The PDN GW (or P-GW) 53 corresponds to the termination point of a datainterface toward a packet data network. The PDN GW 53 can support policyenforcement features, packet filtering, charging support, etc.Furthermore, the PDN GW (or P-GW) 53 can play a role of an anchor pointfor mobility management with a 3GPP network and a non-3GPP network(e.g., an unreliable network, such as an Interworking Wireless LocalArea Network (I-WLAN), a Code Division Multiple Access (CDMA) network,or a reliable network, such as WiMax).

In the network configuration of FIG. 1, the S-GW 52 and the PDN GW 53have been illustrated as being separate gateways, but the two gatewaysmay be implemented in accordance with a single gateway configurationoption.

The MME 51 is an element for performing the access of a terminal to anetwork connection and signaling and control functions for supportingthe allocation, tracking, paging, roaming, handover, etc. of networkresources. The MME 51 controls control plane functions related tosubscribers and session management. The MME 51 manages numerous eNodeBs22 and performs conventional signaling for selecting a gateway forhandover to another 2G/3G networks. Furthermore, the MME 51 performsfunctions, such as security procedures, terminal-to-network sessionhandling, and idle terminal location management.

The SGSN handles all packet data, such as a user's mobility managementand authentication for different access 3GPP networks (e.g., a GPRSnetwork and an UTRAN/GERAN).

The ePDG plays a role of a security node for an unreliable non-3GPPnetwork (e.g., an I-WLAN and a Wi-Fi hotspot).

As described with reference to FIG. 1, a terminal (or UE) having an IPcapability can access an IP service network (e.g., IMS), provided by aservice provider (i.e., an operator), via various elements within an EPCbased on non-3GPP access as well as based on 3GPP access.

Furthermore, FIG. 1 shows various reference points (e.g., S1-U andS1-MME). In a 3GPP system, a conceptual link that connects two functionsthat are present in the different function entities of an E-UTRAN and anEPC is called a reference point. Table 1 below defines reference pointsshown in FIG. 1. In addition to the reference points shown in theexample of Table 1, various reference points may be present depending ona network configuration.

TABLE 1 Reference point Description S1-MME Reference point for thecontrol plane protocol between E-UTRAN and MME S1-U Reference pointbetween E-UTRAN and Serving GW for the per bearer user plane tunnellingand inter eNodeB path switching during handover) S3 It enables user andbearer information exchange for inter 3GPP access network mobility inIdle and/or active state. This reference point can be used intra-PLMN orinter-PLMN (e.g. in the case of Inter-PLMN HO). S4 It provides relatedcontrol and mobility support between GPRS Core and the 3GPP Anchorfunction of Serving GW. In addition, if Direct Tunnel is notestablished, it provides the user plane tunnelling. S5 It provides userplane tunnelling and tunnel management between Serving GW and PDN GW. Itis used for Serving GW relocation due to UE mobility and if the ServingGW needs to connect to a non-collocated PDN GW for the required PDNconnectivity. S11 A reference point between the MME and the S-GW SGi Itis the reference point between the PDN GW and the packet data network.Packet data network may be an operator external public or private packetdata network or an intra operator packet data network, e.g. forprovision of IMS services. This reference point corresponds to Gi for3GPP accesses.

FIG. 2 is an exemplary diagram showing the architecture of a commonE-UTRAN and a common EPC.

As shown in FIG. 2, the eNodeB 20 can perform functions, such as routingto a gateway while RRC connection is activated, the scheduling andtransmission of a paging message, the scheduling and transmission of abroadcast channel (BCH), the dynamic allocation of resources to UE inuplink and downlink, a configuration and providing for the measurementof the eNodeB 20, control of a radio bearer, radio admission control,and connection mobility control. The EPC can perform functions, such asthe generation of paging, the management of an LTE_IDLE state, theciphering of a user plane, control of an EPS bearer, the ciphering ofNAS signaling, and integrity protection.

FIG. 3 is an exemplary diagram showing the structure of a radiointerface protocol in a control plane between UE and an eNodeB, and FIG.4 is another exemplary diagram showing the structure of a radiointerface protocol in a control plane between UE and an eNodeB.

The radio interface protocol is based on a 3GPP radio access networkstandard. The radio interface protocol includes a physical layer, a datalink layer, and a network layer horizontally, and it is divided into auser plane for the transmission of information and a control plane forthe transfer of a control signal (or signaling).

The protocol layers may be classified into a first layer (L1), a secondlayer (L2), and a third layer (L3) based on three lower layers of theOpen System Interconnection (OSI) reference model that is widely knownin communication systems.

The layers of the radio protocol of the control plane shown in FIG. 3and the radio protocol in the user plane of FIG. 4 are described below.

The physical layer PHY, that is, the first layer, provides informationtransfer service using physical channels. The PHY layer is connected toa Medium Access Control (MAC) layer placed in a higher layer through atransport channel, and data is transferred between the MAC layer and thePHY layer through the transport channel. Furthermore, data istransferred between different PHY layers, that is, PHY layers on thesender side and the receiver side, through the PHY layer.

A physical channel is made up of multiple subframes on a time axis andmultiple subcarriers on a frequency axis. Here, one subframe is made upof a plurality of symbols and a plurality of subcarriers on the timeaxis. One subframe is made up of a plurality of resource blocks, and oneresource block is made up of a plurality of symbols and a plurality ofsubcarriers. A Transmission Time Interval (TTI), that is, a unit timeduring which data is transmitted, is 1 ms corresponding to one subframe.

In accordance with 3GPP LTE, physical channels that are present in thephysical layer of the sender side and the receiver side can be dividedinto a Physical Downlink Shared Channel (PDSCH) and a Physical UplinkShared Channel (PUSCH), that is, data channels, and a Physical DownlinkControl Channel (PDCCH), a Physical Control Format Indicator Channel(PCFICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and aPhysical Uplink Control Channel (PUCCH), that is, control channels.

A PCFICH that is transmitted in the first OFDM symbol of a subframecarries a Control Format Indicator (CFI) regarding the number of OFDMsymbols (i.e., the size of a control region) used to send controlchannels within the subframe. A wireless device first receives a CFI ona PCFICH and then monitors PDCCHs.

Unlike a PDCCH, a PCFICH is transmitted through the fixed PCFICHresources of a subframe without using blind decoding.

A PHICH carries positive-acknowledgement (ACK)/negative-acknowledgement(NACK) signals for an uplink (UL) Hybrid Automatic Repeat reQuest(HARQ). ACK/NACK signals for UL data on a PUSCH that is transmitted by awireless device are transmitted on a PHICH.

A Physical Broadcast Channel (PBCH) is transmitted in four former OFDMsymbols of the second slot of the first subframe of a radio frame. ThePBCH carries system information that is essential for a wireless deviceto communicate with an eNodeB, and system information transmittedthrough a PBCH is called a Master Information Block (MIB). In contrast,system information transmitted on a PDSCH indicated by a PDCCH is calleda System Information Block (SIB).

A PDCCH can carry the resource allocation and transport format of adownlink-shared channel (DL-SCH), information about the resourceallocation of an uplink shared channel (UL-SCH), paging information fora PCH, system information for a DL-SCH, the resource allocation of anupper layer control message transmitted on a PDSCH, such as a randomaccess response, a set of transmit power control commands for pieces ofUE within a specific UE group, and the activation of a Voice overInternet Protocol (VoIP). A plurality of PDCCHs can be transmittedwithin the control region, and UE can monitor a plurality of PDCCHs. APDCCH is transmitted on one Control Channel Element (CCE) or anaggregation of multiple contiguous CCEs. A CCE is a logical allocationunit used to provide a PDCCH with a coding rate according to the stateof a radio channel. A CCE corresponds to a plurality of resource elementgroups. The format of a PDCCH and the number of bits of a possible PDCCHare determined by a relationship between the number of CCEs and a codingrate provided by CCEs.

Control information transmitted through a PDCCH is called DownlinkControl Information (DCI). DCI can include the resource allocation of aPDSCH (also called a downlink (DL) grant)), the resource allocation of aPUSCH (also called an uplink (UL) grant), a set of transmit powercontrol commands for pieces of UE within a specific UE group, and/or theactivation of a Voice over Internet Protocol (VoIP).

Several layers are present in the second layer. First, a Medium AccessControl (MAC) layer functions to map various logical channels to varioustransport channels and also plays a role of logical channel multiplexingfor mapping multiple logical channels to one transport channel. The MAClayer is connected to a Radio Link Control (RLC) layer, that is, ahigher layer, through a logical channel. The logical channel isbasically divided into a control channel through which information ofthe control plane is transmitted and a traffic channel through whichinformation of the user plane is transmitted depending on the type oftransmitted information.

The RLC layer of the second layer functions to control a data size thatis suitable for sending, by a lower layer, data received from a higherlayer in a radio section by segmenting and concatenating the data.Furthermore, in order to guarantee various types of QoS required byradio bearers, the RLC layer provides three types of operation modes: aTransparent Mode (TM), an Un-acknowledged Mode (UM), and an AcknowledgedMode (AM). In particular, AM RLC performs a retransmission functionthrough an Automatic Repeat and Request (ARQ) function for reliable datatransmission.

The Packet Data Convergence Protocol (PDCP) layer of the second layerperforms a header compression function for reducing the size of an IPpacket header containing control information that is relatively large insize and unnecessary in order to efficiently send an IP packet, such asIPv4 or IPv6, in a radio section having a small bandwidth when sendingthe IP packet. Accordingly, transmission efficiency of the radio sectioncan be increased because only essential information is transmitted inthe header part of data. Furthermore, in an LTE system, the PDCP layeralso performs a security function. The security function includesciphering for preventing the interception of data by a third party andintegrity protection for preventing the manipulation of data by a thirdparty.

A Radio Resource Control (RRC) layer at the highest place of the thirdlayer is defined only in the control plane and is responsible forcontrol of logical channels, transport channels, and physical channelsin relation to the configuration, re-configuration, and release of RadioBearers (RBs). Here, the RB means service provided by the second layerin order to transfer data between UE and an E-UTRAN.

If an RRC connection is present between the RRC layer of UE and the RRClayer of a wireless network, the UE is in an RRC_CONNECTED state. Ifnot, the UE is in an RRC_IDLE state.

An RRC state and an RRC connection method of UE are described below. TheRRC state means whether or not the RRC layer of UE has been logicallyconnected to the RRC layer of an E-UTRAN. If the RRC layer of UE islogically connected to the RRC layer of an E-UTRAN, it is called theRRC_CONNECTED state. If the RRC layer of UE is not logically connectedto the RRC layer of an E-UTRAN, it is called the RRC_IDLE state. SinceUE in the RRC_CONNECTED state has an RRC connection, an E-UTRAN cancheck the existence of the UE in a cell unit, and thus control the UEeffectively. In contrast, if UE is in the RRC_IDLE state, an E-UTRANcannot check the existence of the UE, and a core network is managed in aTracking Area (TA) unit, that is, an area unit greater than a cell. Thatis, only the existence of UE in the RRC_IDLE state is checked in an areaunit greater than a cell. In such a case, the UE needs to shift to theRRC_CONNECTED state in order to be provided with common mobilecommunication service, such as voice or data. Each TA is classifiedthrough Tracking Area Identity (TAI). UE can configure TAI throughTracking Area Code (TAC), that is, information broadcasted by a cell.

When a user first turns on the power of UE, the UE first searches for aproper cell, establishes an RRC connection in the corresponding cell,and registers information about the UE with a core network. Thereafter,the UE stays in the RRC_IDLE state. The UE in the RRC_IDLE state(re)selects a cell if necessary and checks system information or paginginformation. This process is called camp on. When the UE in the RRC_IDLEstate needs to establish an RRC connection, the UE establishes an RRCconnection with the RRC layer of an E-UTRAN through an RRC connectionprocedure and shifts to the RRC_CONNECTED state. A case where the UE inthe RRC_IDLE state needs to establish with an RRC connection includesmultiple cases. The multiple cases may include, for example, a casewhere UL data needs to be transmitted for a reason, such as a callattempt made by a user and a case where a response message needs to betransmitted in response to a paging message received from an E-UTRAN.

A Non-Access Stratum (NAS) layer placed over the RRC layer performsfunctions, such as session management and mobility management.

The NAS layer shown in FIG. 3 is described in detail below.

Evolved Session Management (ESM) belonging to the NAS layer performsfunctions, such as the management of default bearers and the managementof dedicated bearers, and ESM is responsible for control that isnecessary for UE to use PS service from a network. Default bearerresources are characterized in that they are allocated by a network whenUE first accesses a specific Packet Data Network (PDN) or accesses anetwork. Here, the network allocates an IP address available for UE sothat the UE can use data service and the QoS of a default bearer. LTEsupports two types of bearers: a bearer having Guaranteed Bit Rate (GBR)QoS characteristic that guarantees a specific bandwidth for thetransmission and reception of data and a non-GBR bearer having the besteffort QoS characteristic without guaranteeing a bandwidth. A defaultbearer is assigned a non-GBR bearer, and a dedicated bearer may beassigned a bearer having a GBR or non-GBR QoS characteristic.

In a network, a bearer assigned to UE is called an Evolved PacketService (EPS) bearer. When assigning an EPS bearer, a network assignsone ID. This is called an EPS bearer ID. One EPS bearer has QoScharacteristics of a Maximum Bit Rate (MBR) and a Guaranteed Bit Rate(GBR) or an Aggregated Maximum Bit Rate (AMBR).

FIG. 5 is a flowchart illustrating a random access process in 3GPP LTE.

The random access process is used for UE 10 to obtain UL synchronizationwith a base station, that is, an eNodeB 20, or to be assigned UL radioresources.

The UE 10 receives a root index and a physical random access channel(PRACH) configuration index from the eNodeB 20. 64 candidate randomaccess preambles defined by a Zadoff-Chu (ZC) sequence are present ineach cell. The root index is a logical index that is used for the UE togenerate the 64 candidate random access preambles.

The transmission of a random access preamble is limited to specific timeand frequency resources in each cell. The PRACH configuration indexindicates a specific subframe on which a random access preamble can betransmitted and a preamble format.

The UE 10 sends a randomly selected random access preamble to the eNodeB20. Here, the UE 10 selects one of the 64 candidate random accesspreambles. Furthermore, the UE selects a subframe corresponding to thePRACH configuration index. The UE 10 sends the selected random accesspreamble in the selected subframe.

The eNodeB 20 that has received the random access preamble sends aRandom Access Response (RAR) to the UE 10. The random access response isdetected in two steps. First, the UE 10 detects a PDCCH masked with arandom access-RNTI (RA-RNTI). The UE 10 receives a random accessresponse within a Medium Access Control (MAC) Protocol Data Unit (PDU)on a PDSCH that is indicated by the detected PDCCH.

Meanwhile, an E-UTRAN which is a radio access network for 4^(th)generation (4G) mobile communication requires high costs, and thus isnot widespread as fast as expected. Therefore, a UTRAN which is a radioaccess network for 3^(rd) generation (3G) mobile communication and theE-UTRAN which is the radio access network for the 4G mobilecommunication may coexist. In such a situation, if a UE moves back andforth between the E-UTRAN and the UTRAN, a location registrationfrequently occurs. The frequent location registration leads to anincrease in network signaling, which results in an introduction of anidle mode signaling reduction (ISR) scheme. In the ISR scheme, if the UEin an idle mode has moved back and forth one time between the E-UTRANand the UTRAN and thus the location registration has been alreadyachieved, the location registration may not be performed when the UEmoves next time.

On the other hand, an increase in a user requirement for a socialnetwork service (SNS) results in a growing increase in a demand forproximity communication between physically adjacent UEs. Therefore,there is an ongoing discussion that the proximity communication betweenthe UEs will be employed in a next generation system. However, adiscovery between the UEs is necessary for the proximity communicationbetween the UEs. Although the discovery may be performed directlybetween the UEs, it may also be performed with the assistance of thenetwork.

Disadvantageously, when the aforementioned ISR is activated, since thelocation registration is not performed even if the UE in the idle modemoves back and forth between the E-UTRAN and the UTRAN, there is aproblem in that the discovery between the UEs is not properly performedwith the assistance of the network.

SUMMARY OF THE INVENTION

Accordingly, a disclosure of the present specification aims to provide amethod capable of solving the aforementioned problem.

To acheive the aforementioned aim, a disclosure of the presentspecification provides a method of determining whether to activate anidle mode signaling reduction (ISR) capability in a network entity formanaging mobility of a user equipment (UE). The method may comprise:obtaining information related to a proximity service of the UE;receiving from the UE a location update request message; determiningwhether to activate the ISR on the basis of ISR capability informationof a network node by which the UE has been served just previously, ISRcapability information of the network entity, and information related tothe proximity service of the UE; and transmitting a location updateaccept message to the UE after the determination.

The location update request message may be a tracking area update (TAU)request message or a routing area update (RAU) request message.

The information related to the proximity service of the UE may compriseone or more of: capability information for the proximity service of theUE; proximity service enable state information of the UE; informationregarding whether the UE is in a state capable of performing theproximity service or is scheduled to perform the proximity service; andinformation regarding a network-assisted discovery.

The information regarding the network-assisted discovery may compriseone or more of: information regarding whether the UE is a UE of asubscriber capable of using the network-assisted discovery service; andinformation regarding whether a specific service is in a state in whichthe network-assisted discovery service is allowed for use.

The method may further comprise: upon receiving the location updaterequest message, transmitting a request message for a context of the UEto a network by which the UE has been served just previously; andreceiving a context response message from the network node. Here, thecontext response message comprises information regarding an ISRcapability of the network node.

The determining may comprise one or more of: confirming whether both ofthe network entity and the network node have an ISR capability on thebasis of the ISR capability information of the network node and the ISRcapability information of the network entity; confirming whether the UEis scheduled to perform the proximity service; and confirming whether anetwork-assisted discovery is scheduled to be performed.

In the determining, even if it is confirmed that both of the networkentity and the network node have the ISR capability, the ISR may bedetermined to be deactivated when it is confirmed that the UE isscheduled to perform the proximity service and the network-assisteddiscovery is scheduled to be performed.

If the determination result shows that the ISR is not activated, thelocation update accept message comprises an update result indicatingthat only a location update is performed.

The network entity may be a mobile management entity (MME), and thenetwork node by which the UE has been served just previously may be aserving general packet radio service support node (SGSN).

Meanwhile, a disclosure of the present specification also provides amethod of determining whether to activate an idle mode signalingreduction (ISR) capability in a network entity for managing mobility ofa user equipment (UE). The method may comprise: receiving by the networkentity a context request message from a network node for newly servingthe UE; determining whether there is an ISR capability to be included ina context response message in response to the context request message onthe basis of information related to the proximity service of the UE; andtransmitting to the network node the context response message generateddepending on the determination.

The information related to the proximity service of the UE comprises oneor more of: capability information regarding the proximity service ofthe UE; proximity service enable state information of the UE;information regarding whether the UE is in a state capable performingthe proximity service or is scheduled to perform the proximity service;and information regarding a network-assisted discovery.

In the determining of whether there is the ISR capability, if it isconfirmed that the UE is scheduled to perform the proximity service andthe network-assisted discovery is scheduled to be performed, even if thenetwork entity supports the ISR capability, the context response messageis configured not to support the ISR capability.

If the network entity is a mobility management entity (MME), the networknode is a serving general packet radio service support node (SGSN), andif the network entity is the SGSN, the network node is the MME.

According to a disclosure of the present specification, an idle modesignaling reduction (ISR) capability is deactivated for a proximityservice, and thus a correct discovery is possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the configuration of an evolved mobile communicationnetwork.

FIG. 2 is an exemplary diagram showing the architecture of a commonE-UTRAN and a common EPC.

FIG. 3 is an exemplary diagram showing the structure of a radiointerface protocol in a control plane between a UE and an eNodeB.

FIG. 4 is another exemplary diagram showing the structure of a radiointerface protocol in a control plane between a UE and an eNodeB.

FIG. 5 is a flowchart illustrating a random access process in 3GPP LTE.

FIG. 6 shows a situation where a UTRAN and an E-UTRAN coexist.

FIG. 7 is a flowchart illustrating an idle mode signalign reduction(ISR) for solving the problem of FIG. 6.

FIG. 8a shows an example of a typical communication.

FIG. 8b shows the concept of proximity communication expected to beemployed in a next-generation communication system.

FIG. 9a is an exemplary diagram showing an example of proximitycommunication.

FIG. 9b is an exemplary diagram showing another example of proximitycommunication.

FIG. 10 shows an example of using a secure user plane location (SUPL)service for a ProSe discovery.

FIG. 11 shows a ProSe discovery procedure using an SUPL service.

FIG. 12 is a flowchart illustrating a solution according to a firstexample of a first method.

FIG. 13 is a flowchart illustrating a solution according to a secondexample of a first method.

FIG. 14 is a flowchart illustrating a solution according to a firstexample of a second method.

FIG. 15 is a block diagram of an SGSN 420 and an MME 510 according to adisclosure of the present specification.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention is described in light of UMTS (Universal MobileTelecommunication System) and EPC (Evolved Packet Core), but not limitedto such communication systems, and may be rather applicable to allcommunication systems and methods to which the technical spirit of thepresent invention may apply.

The technical terms used herein are used to merely describe specificembodiments and should not be construed as limiting the presentinvention. Further, the technical terms used herein should be, unlessdefined otherwise, interpreted as having meanings generally understoodby those skilled in the art but not too broadly or too narrowly.Further, the technical terms used herein, which are determined not toexactly represent the spirit of the invention, should be replaced by orunderstood by such technical terms as being able to be exactlyunderstood by those skilled in the art. Further, the general terms usedherein should be interpreted in the context as defined in thedictionary, but not in an excessively narrowed manner.

The expression of the singular number in the specification includes themeaning of the plural number unless the meaning of the singular numberis definitely different from that of the plural number in the context.In the following description, the term ‘include’ or ‘have’ may representthe existence of a feature, a number, a step, an operation, a component,a part or the combination thereof described in the specification, andmay not exclude the existence or addition of another feature, anothernumber, another step, another operation, another component, another partor the combination thereof.

The terms ‘first’ and ‘second’ are used for the purpose of explanationabout various components, and the components are not limited to theterms ‘first’ and ‘second’. The terms ‘first’ and ‘second’ are only usedto distinguish one component from another component. For example, afirst component may be named as a second component without deviatingfrom the scope of the present invention.

It will be understood that when an element or layer is referred to asbeing “connected to” or “coupled to” another element or layer, it can bedirectly connected or coupled to the other element or layer orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly connected to” or “directlycoupled to” another element or layer, there are no intervening elementsor layers present.

Hereinafter, exemplary embodiments of the present invention will bedescribed in greater detail with reference to the accompanying drawings.In describing the present invention, for ease of understanding, the samereference numerals are used to denote the same components throughout thedrawings, and repetitive description on the same components will beomitted. Detailed description on well-known arts which are determined tomake the gist of the invention unclear will be omitted. The accompanyingdrawings are provided to merely make the spirit of the invention readilyunderstood, but not should be intended to be limiting of the invention.It should be understood that the spirit of the invention may be expandedto its modifications, replacements or equivalents in addition to what isshown in the drawings.

In the drawings, user equipments (UEs) are shown for example. The UE mayalso be denoted a terminal or mobile equipment (ME). The UE may be alaptop computer, a mobile phone, a PDA, a smartphone, a multimediadevice, or other portable device, or may be a stationary device such asa PC or a car mounted device.

DEFINITION OF TERMS

For a better understanding, the terms used herein are briefly definedbefore going to the detailed description of the invention with referenceto the accompanying drawings.

A GERAN is an abbreviation of a GSM EDGE Radio Access Network, and itrefers to a radio access section that connects a core network and UE byGSM/EDGE.

A UTRAN is an abbreviation of a Universal Terrestrial Radio AccessNetwork, and it refers to a radio access section that connects the corenetwork of the 3rd generation mobile communication and UE.

An E-UTRAN is an abbreviation of an Evolved Universal Terrestrial RadioAccess Network, and it refers to a radio access section that connectsthe core network of the 4th generation mobile communication, that is,LTE, and UE.

An UMTS is an abbreviation of a Universal Mobile TelecommunicationSystem, and it refers to the core network of the 3rd generation mobilecommunication.

UE or an MS is an abbreviation of User Equipment or a Mobile Station,and it refers to a terminal device.

An EPS is an abbreviation of an Evolved Packet System, and it refers toa core network supporting a Long Term Evolution (LTE) network and to anetwork evolved from an UMTS.

A PDN is an abbreviation of a Public Data Network, and it refers to anindependent network where a service for providing service is placed.

A PDN connection refers to a connection from UE to a PDN, that is, anassociation (or connection) between UE represented by an IP address anda PDN represented by an APN.

A PDN-GW is an abbreviation of a Packet Data Network Gateway, and itrefers to a network node of an EPS network which performs functions,such as the allocation of a UE IP address, packet screening & filtering,and the collection of charging data.

A Serving gateway (Serving GW) is a network node of an EPS network whichperforms functions, such as mobility anchor, packet routing, idle modepacket buffering, and triggering an MME to page UE.

An Access Point Name (APN) is the name of an access point that ismanaged in a network and provides to UE. That is, an APN is a characterstring that denotes or identifies a PDN. Requested service or a network(PDN) is accessed via a P-GW. An APN is a name (character string, e.g.,‘internet.mnc012.mcc345.gprs’) previously defined within a network sothat the P-GW can be searched for.

A NodeB is an eNodeB of a UMTS network and installed outdoors. The cellcoverage of the NodeB corresponds to a macro cell.

An eNodeB is an eNodeB of an Evolved Packet System (EPS) and isinstalled outdoors. The cell coverage of the eNodeB corresponds to amacro cell.

An (e)NodeB is a term that denotes a NodeB and an eNodeB.

An MME is an abbreviation of a Mobility Management Entity, and itfunctions to control each entity within an EPS in order to provide asession and mobility for UE.

A session is a passage for data transmission, and a unit thereof may bea PDN, a bearer, or an IP flow unit. The units may be classified into aunit of the entire target network (i.e., an APN or PDN unit) as definedin 3GPP, a unit (i.e., a bearer unit) classified based on QoS within theentire target network, and a destination IP address unit.

A PDN connection is a connection from UE to a PDN, that is, anassociation (or connection) between UE represented by an IP address anda PDN represented by an APN. It means a connection between entities(i.e., UE-PDN GW) within a core network so that a session can be formed.

UE context is information about the situation of UE which is used tomanage the UE in a network, that is, situation information including anUE ID, mobility (e.g., a current location), and the attributes of asession (e.g., QoS and priority)

A Non-Access-Stratum (NAS) is a higher stratum of a control planebetween UE and an MME. The NAS supports mobility management and sessionmanagement between UE and a network, IP address maintenance, and so on.

RAT is an abbreviation of Radio Access Technology, and it means a GERAN,a UTRAN, or an E-UTRAN.

Proximity service (Proximity Service, ProSe Service or Proximity basedService): means discovery and mutually direct communication betweenphysically adjacent UEs. However, the proximity service is a conceptincluding communication between UEs through a base station and,furthermore, a concept including communication between UEs through athird UE. Here, data on a user plane is exchanged through a direct datapath without passing through a 3GPP core network (e.g. EPC).

Proximity: That a UE is located in close proximity to another UE meanswhen a predetermined proximity condition is met. A proximity conditionfor discovery may be different from a proximity condition forcommunication.

Range Class: means a rough distance range as a use for ProSe discovery,for example, a geographical distance range, and a distance range as acommunication condition.

ProSe-enabled UE: means a UE supporting ProSe discovery, ProSecommunication and/or ProSe-supported WLAN direct communication. In thepresent specification, the ProSe-enabled UE is also referred to as UEsimply.

Announcing UE: a UE that notifies of information that can be used byadjacent UEs having discovery rights.

Monitoring UE: a UE that receives interested information from otheradjacent UEs.

ProSe-enabled Network: means a network supporting ProSe discovery, ProSecommunication and/or ProSe-supported WLAN direct communication. In thepresent specification, the ProSe-enabled Network is also referred to asnetwork simply.

ProSe discovery: refers to a process of discovering a ProSe-enabled UEwhen it is closely located.

Open ProSe Discovery: means that it is possible to discover aProSe-enabled UE without a direct permission when detecting it.

Restricted ProSe Discovery: means that it is possible to discover aProSe-enabled UE only with a direct permission when detecting it.

ProSe Communication: means performing communication between UEs using anE-UTRAN communication path when a ProSe-enabled UE is closely located. Acommunication path may be established, for example, directly between UEsor via a local (or neighbor) eNodeB.

ProSe Group Communication: means performing one-to-all groupcommunication using a common communication path established between twoor more ProSe-enabled UEs when they are located adjacent to each other.

ProSe E-UTRA communication: means ProSe communication using an E-UTRAcommunication path.

ProSe-assisted WLAN direct communication: means ProSe communicationusing a WLAN direct communication path.

ProSe communication path: means a communication path supporting ProSecommunication. A path of the ProSe E-UTRA communication can beestablished directly between ProSe-enabled UEs by using an E-UTRA or aneNodeB. A path of the ProSe-assisted WLAN direct communication can beestablished directly between the ProSe-enabled UEs via a WLAN.

EPC path (or infrastructure data path): mans a communication path of auser plane via EPC.

ProSe UE-to-network relay: means a relay which plays a role of acommunication relay between a ProSe-enabled network and a ProSe-enabledUE.

ProSe UE-to-UE relay: means a relay which plays a role of acommunication relay between ProSe-enabled UEs.

ISR (idle mode signaling reduction): means a scheme of reducing a wasteof network resources caused by a repetitive location registrationprocedure when a UE frequently moves back and forth between an E-UTRANand a UTRAN (or GERAN).

Meanwhile, following descriptions will be made with reference to theaccompanying drawings.

FIG. 6 shows a situation where a UTRAN and an E-UTRAN coexist.

As can be seen from FIG. 6, an eNodeB of the E-UTRAN (i.e., a 4G radioaccess network) may be deployed in a region in which a NodeB of theUTRAN (i.e., a 3G radio access network) exists.

A tracking area identity (TAI) list illustrated herein indicates an areain which the E-UTRAN provides a service in unit of an E-UTRAN locationregistration, and includes a cell of one or a plurality of eNodeBs.

In addition, a routing area (RA) illustrated herein indicates an area inwhich the UTRAN provides a service in unit of a UTRAN locationregistration, and includes a cell of one or a plurality of NodeBs.

A UE 100 illustrated herein is located at a boundary of the E-UTRAN andthe UTARN, and may camp on any one of them. Herein, the camp-on impliesthat the UE 100 accesses a cell after finishing a cell selectionprocedure or a cell reselection procedure. If the UE 100 camps on anE-UTRAN cell, a location registration to an MME 510 is performed, and ifthe UE 100 camps on a UTRAN cell, a location registration to a servinggeneral packet radio service support node (SGSN) 420 is performed.

However, as illustrated, if the UE 100 is located in the boundary of theE-UTRAN and the UTRAN, an unexpected cell reselection procedure isrepeated and thus a location registration procedure is continuouslyperformed, which may result in a waste of network resources.

FIG. 7 is a flowchart illustrating an idle mode signalign reduction(ISR) for solving the problem of FIG. 6.

The ISR is a scheme for increasing efficiency of a network resource byreducing signaling for a location registration when a UE 100 moves backand forth between an E-UTRAN and a UTRAN. In the ISR scheme, if the UE100 in an idle mode has moved back and forth one time between theE-UTRAN and the UTRAN and thus the location registration has beenalready achieved, the location registration may not be performed whenthe UE moves next time.

Detailed descriptions thereof are as follows.

Referring to FIG. 7, a UE 100 first camps on an E-UTRAN cell, and thusthe UE 100 sends an attach request message to perform a locationregistration to an HSS 540 via an MME 510. The MME 510 sends an updatelocation request message to report to the HSS 540 that the UE 100 isattached.

In this case, the HSS 540 stores an identity (ID) of the MME 510 towhich the UE 100 is attached, and sends an update location ACK messagecontaining subscriber information to the MME 510 as a response. The MME510 sends an attach accept message to the UE 100. Accordingly, the UE100 completes an attach procedure on the MME 510 of the E-UTRAN cell onwhich the UE 100 camps

Thereafter, it is assumed that the UE 100 moves from the E-UTRAN cell toa coverage area of a UTRAN cell. In this case, the UE 100 reselects theUTRAN. Therefore, the UE 100 must register its location to the UTRAN byperforming a routing area update (RAU) procedure.

Accordingly, the UE 100 sends an RAU request message to a servinggeneral packet radio service support node (SGSN) 420 to perform alocation registration to the HSS 540 via the SGSN 420. The SGSN 420recognizes from the RAU request message that the UE 100 has previouslyperformed the location registration to the MME 510. Therefore, the SGSN420 sends a context request message to the MME 510 to acquire a contextfor the UE 100 from the MME 510 to which the UE 100 has performed thelocation registration.

In response to the context request message sent by the SGSN 420, the MME510 sends a context response message containing the context for the UE100 to the SGSN 420. In this case, the MME 510 inserts a parameter ‘ISRcapability’ or ‘ISR supported’ into the context response message, andthus reports to the SGSN 420 that the MME 510 can support the ISRcapability. Meanwhile, context information for the UE 100 and includedin the context response message representatively includes UE's mobilitymanagement (MM) context information and EPS PDN connections information.Herein, the EPS PDN connections information includes bearer contextinformation. The MME 510 sets the context information for the UE 100 andto be included in the context response message on the basis of the MMcontext and EPS bearer context information for the UE 100 and maintainedin the MME 510.

The SGSN 420 determines whether the ISR will be activated for the UE100. More specifically, the SGSN 420 may analyze or confirm theparameter ‘ISR capability’ or ‘ISR supported’ of the context responsemessage received from the MME 510, and thus confirm that the MME 510supports the ISR capability. In addition, since the SGSN 420 alsosupports the ISR capability, the SGSN 420 determines to activate theISR.

The SGSN 420 determines the activation of the ISR capability. Therefore,the SGSN 420 sends a context ACK message to the MME 510 in response tothe context response message sent by the MME 510. In this case, aparameter ‘ISR activated’ is inserted to the context ACK message so asto report to the MME 510 that the ISR capability is activated for the UE100.

Meanwhile, if the ISR is activated, the SGSN 420 and the MME 510 storemutual identities (IDs). In addition, the MME 510 which has received thecontext ACK message including the parameter ‘ISR activated’ from theSGSN 420 continuously maintains the context for the UE 100.

The SGSN 420 sends an update location request message to the HSS 540 toreport the location registration of the UE 100. In addition, the HSS 540stores an ID of the SGSN 420 for which the UE 100 performs the RAU, andsends an update location ACK message containing subscriber informationof the UE 100 to the SGSN 420 as a response.

The SGSN 420 sends an RAU accept message to the UE 100. In this case, aparameter ‘ISR activated’ is inserted to the RAU accept message so as toreport that the ISR capability is activated for the UE 100.

It is described above that the location of the UE is registered throughthe attach procedure and the RAU procedure. Further, the MME 510 and theSGSN 420 support the ISR capability, and thus the ISR is activated.

Therefore, even if the UE 100 moves again from the UTRAN to the E-UTRANand thus the E-UTRAN cell is reselected, the UE 100 does not have toperform the location registration to the MME 510 since the ISR iscurrently activated.

That is, after the ISR is activated, the location registration to thenetwork is not necessarily performed again as long as the UE 100 iswithin a routing area (RA) registered through the SGSN 420 and atracking area identity (TAI) list registered through the MME 510. Thiscapability is the ISR. Meanwhile, the RA registered through the SGSN 420and the TAI list registered through the MME 510 are referred to togetheras an ISR area. As described above, if the UE frequently moves betweenthe E-UTRAN and the UTRAN/GERAN, the ISR capability can reduce a wasteof network resources by avoiding a repetitive location registrationprocedure.

FIG. 8a shows an example of a typical communication.

Referring to FIG. 8a , a UE#1 100-1 exists within a coverage of aneNodeB#1 200-1, and a UE#2 100-2 exists within a coverage of an eNodeB#2200-2. Communication between the UE#1 100-1 and the UE#2 100-2 may beperformed via a core network, for example, an S-GW 520/P-GW 530. Assuch, a communication path which passes through the core network may becalled an infrastructure data path. In addition, communication performedvia the infrastructure data path is called infrastructure communication.

FIG. 8b shows the concept of proximity communication expected to beemployed in a next-generation communication system.

An increase in a user requirement for a social network service (SNS)results in the arising of a demand for a discovery between physicallyadjacent UEs and special applications/services, i.e., proximity-basedapplication/services. Therefore, there is a growing increase in a demandfor proximity communication between UEs.

In order to apply the aforementioned requirement, as illustrated in FIG.8b , there is an ongoing discussion on a method capable of performing adirectly communication among a UE#1 100-1, a UE#2 100-2, and a UE#3100-3 or among a UE#4 100-4, a UE#5 100-5, and a UE#6 100-6 without anintervention of an eNodeB 200. Of course, communication may be achieveddirectly between the UE#1 100-1 and the UE#4 100-4 with the assistanceof the eNodeB 200. Meanwhile, the UE#1 100-1 may play a role of a relayfor the UE#2 100-2 and the UE#3 100-3 located far from a cell center.Likewise, the UE#4 100-4 may play a role of a relay for the UE#5 100-5and the UE#6 100-6 located far from the cell center.

As described above, there is an ongoing discussion that thenext-generation system will employ proximity communication between UEs.

FIG. 9a is an exemplary diagram showing an example of proximitycommunication, and FIG. 9b is an exemplary diagram showing anotherexample of proximity communication.

Referring to FIG. 9a , there is illustrated a situation that a UE#1100-1 and a UE#2 100-2 perform proximity communication through a directcommunication path while camping on different eNodeBs, respectively.Referring to FIG. 9b , there is shown a situation that a UE#1 100-1 anda UE#2 100-2 perform proximity communication through a directcommunication path while camping on an eNodeB 200, respectively.

As such, the UE#1 100-1 and the UE#2 100-2 may perform proximitycommunication through a direct communication path bypassing a paththrough an eNodeB and a core network that a service provider operates.

The term, direct communication path, may be variously referred to asdata path for proximity service, data path based on proximity service orproximity service communication path. Furthermore, communication throughthe direct communication path may be variously called directcommunication, proximity service communication or proximityservice-based communication.

FIG. 10 shows an example of using a secure user plane location (SUPL)service for a ProSe discovery.

The SUPL service is a service for providing a location service through auser plane. A location of a UE 100 is calculated by using triangulationthrough a plurality of eNodeBs or GPS-assisted triangulation. An SUPLlocation platform (SLP) 700 illustrated herein accesses an EPC toacquire location information of the UE 100 from the eNodeB or to acquirea GPS-based location from the UE 100, and plays a role of delivering theacquired location information to a requester. Hereinafter, a ProSediscovery procedure using the SUPL service will be described in greaterdetail with reference to FIG. 11.

FIG. 11 shows a ProSe discovery procedure using a secure user planelocation (SUPL) service.

Referring to FIG. 11, it is shown a procedure in which a UE-A 100 adiscovers a UE-B 100 b by the aid of a network, that is, by using theSUPL service.

(1) First, the UE-A 100 a transmits a proximity request to a ProSefunction server A 810 a. The proximity request may include an EPUID_A,an application ID, an ALUID_A, an ALUID_B, a window, a range, andlocation information of the UE-A 100. In addition, the proximity requestmay selectively include a WLAN ID. The application ID identifies anapplication platform server. The ALUID_A and the ALUID_B are IDs foridentifying the UE-A 100 a and the UE-B 100 b, respectively. The windowimplies a time duration in which the proximity request is valid. Therange indicates a range class requested for the application amongallowed range class sets. The location information indicates a UElocation known to the UE-A 100A. The WLAN ID may be included when theUE-A 100A selectively requests a WLAN direct discovery.

(2) The ProSe function server A 810 a transmits a MAP request to anapplication server 850 to acquire a ProSe subscriber ID of the UE-B 100b. The MAP request includes the ALUID_A and the ALUID_B. In this case,the ProSe function server A 810 a stores IDs of the UE-A 100 a and theUE-B 100 b in the application, i.e., the ALUID_A and the ALUID_B, for aduration indicated in the window.

(3) The application server 850 confirms whether ProSe is allowed in theapplication of the UE-B 100 b, confirms whether the UE-B 100 b allowsthe UE-A 100 a to discover the UE-B 100 b, and thereafter transmits aMAP response to the ProSe function server A 810 a. The MAP responseincludes an EPC ProSe subscriber ID of the UE-B 100 b (i.e., EPUIC_B) ofthe UE-B 100 b and an ID of a ProSe function server B 810 b (i.e.,PFID_B). Then, the ProSe function server A 810 a stores the EPUID_B andthe PFID_B.

(4) The ProSe function server A 810 a delivers a proximity request tothe ProSe function server B 810 b in order to request a periodic updateof a location. The proximity request may include the EPUIC_B, theEPUIC_A, the window, and the location information of the UE-A 100 a.Alternatively, the proximity request may include the WLAN ID.

(5) The ProSe function server B 810 b confirms a record of the UE-B 100b on the basis of the EPUID_B. That is, the ProSe function server B 810b may request an HSS 540 to provide information regarding a lastlocation of the UE-B 100 b. The ProSe function server B 810 b maydetermine whether it is in proximity to the UE-A 100 a and the UE-B 100b on the basis of the location of the UE-B 100 b and the location of theUE-A 100 a. If it is confirmed that it is not in proximity to the UE-A100 a and the UE-B 100 b for the duration indicated in the window, theProSe function server B 810 b may transmit a proximity request rejectmessage to the ProSe function server A 810 a in order to reject theproximity request. In response thereto, the ProSe function server A 810a may deliver the proximity request reject message to the UE-A 100 a.

(6) Meanwhile, according to a ProSe configuration (or profile) of theUE-B 100 b, the UE-B 100 b may receive a confirmation request as towhether to accept the proximity request.

(7) The ProSe function server B 810 b transmits an LCS locationreporting request message of the UE-B 100 b to an SLP-B 700 b. Inaddition, the ProSe function server B 810 b transmits a proximityrequest ACK message to the ProSe function server A 810 a. The proximityrequest ACK message may include a location of the UE-B. The proximityrequest ACK message may further include a WLAN ID of the UE-B.

(8) The ProSe function server A 810 a transmits an LCS locationreporting request message of the UE-A 100 a to an SPL-A 700 a. If it isconfirmed that it is not in proximity to the UE-A 100 a and the UE-B 100b for the duration indicated in the window, the ProSe function server A810 a may determine whether to cancel the proximity request. Otherwise,the ProSe function server A 810 a transmits the proximity request ACKmessage to the UE-A 100 a.

As described above, the ProSe discovery may use the SUPL service.However, if the ISR described with reference to FIG. 7 is activated, theUE-B 100 b does not perform RAU or TAU, and thus the HSS 540 cannot knowinformation regarding a correct last location of the UE-B 100 b.Therefore, there is a problem in that the ProSe function server B 810 bcannot correctly determine whether it is in proximity to the UE-A 100 aand the UE-B 100 b.

This problem will be described in greater detail as follows. In case ofa network-assisted discovery, i.e., an EPC-level ProSe discovery, thereis a need to acquire information regarding a recent location of the UE-B100 b which is a target of the discovery from a network, for example,the HSS 540. However, if the ISR is applied, since the UE-B 100 b whichis the target of the discovery does not perform the RAU or the TAU, thenetwork, i.e., the HSS 540, does not have information indicating whetherthe UE-B 100 b is currently in the E-UTRAN or in the UTRAN/GERAN.

In particular, returning to FIG. 7, if the update location requestmessage is received from the MME 510 or the SGSN 420 according to theTAU/RAU, the HSS 540 simply registers the MME 510 and the SGSN 420, andhas information as shown in Table 2 below. That is, whether the UE-B 100b is currently in the E-UTRAN or in the UTRAN/GERAN can be known on thebasis of the information shown in Table 2.

TABLE 2 MME Identity An identity of an MME serving a UE-B SGSN AddressAn address of an SGSN serving a UE-B

However, if the ISR is applied and thus the UE-B 100 b does not performthe RAU/TAU, eventually, whether the UE-B 100 b is currently in theE-UTRAN or in the UTRAN/GERAN cannot be correctly known. That is, it isdifficult for the HSS 540 to determine whether the UE-B 100 b is in anE-UTRAN coverage in which a ProSe service is currently available (i.e.,a TAU area served by the MME) or is out of the coverage (i.e., aUTRAN/GERAN RAU/LAU area served by the SGSN, and in a normal case, arange of an area served by the SGSN is wide, and there may be a rangeoverlapping with the TAU area and a range not overlapping therewith). Ingeneral, the HSS 540 may have a MAP of an operator's network mapped toan MME ID/SGSN address, and may use corresponding information to roughlyestimate a proximity between the UE-A 100 a and the UE-B 100 b whichhave transmitted a proximity request. However, if the ISR is activated,in which area the UE-B 100 b is currently located cannot be known, andthus it is difficult to estimate the proximity.

Accordingly, disclosures of the present specification propose methodsfor solving the aforementioned problem.

Brief Description on Disclosures of the Present Specification

The disclosures of the present specification proposes methods foreffectively performing a discovery for a proximity service in a mobilecommunication system such as a 3GPP evolved packet system (EPS).

Specifically, the disclosure of the present specification proposesmethods for allowing an ISR not to be activated for a proximity serviceor for deactivating an activated ISR.

First, the methods for allowing the ISR not to be activated for theproximity service will be described as follows. According to a firstexample of the first method, when determining whether a network node,e.g., an MME, will activate the ISR, it is determined by using aparameter related to the proximity service. According to a secondexample of the first method, in order to prevent the ISR from beingactivated between network nodes, mutually manipulated information (i.e.,even if an ISR capability is present, it is manipulated as being notpresent) is exchanged. In the determining of whether network nodes willmanipulate the information, the parameter related to the proximityservice may be used.

Second, the method of deactivating the activated ISR will be describedas follows. According to a first example of the second method, a networknode may actively instruct a UE to deactivate the activated ISR.According to a second example of the second method, each of networknodes may deactivate the ISR and thereafter may exchange informationthereon. According to a third example of the second method, it may bemutually requested to deactivate the ISR between the network nodes.

Hereinafter, disclosures of the present specification will be describedwith reference to the accompanying drawings.

FIG. 12 is a flowchart illustrating a solution according to a firstexample of a first method.

A method shown in FIG. 12 is a method in which a parameter related to aproximity service is used when determining whether the network node,e.g., the MME, will activate an ISR according to the first example ofthe first method described above. Detailed descriptions thereof are asfollows.

(1)˜(2) A UE-B 100 b selects a UTRAN and performs an attach procedurewith respect to an SGSN-B 420 b.

(3)˜(4) If the UE-B 100 b selects an EUTRAN, the UE-B 100 b transmits aTAU request message to an MME-B 510 b serving the UE-B 100 b.

(5) Then, the MME-B 510 b acquires ProSe related information. The ProSerelated information may include information regarding whether the UE-B100 b has a ProSe capability and information regarding whether the UE-B100 b enables the ProSe service. Alternatively, the ProSe relatedinformation may include information regarding whether an EPC-level ProSediscovery can be used.

The information regarding the EPC-level ProSe discovery may includeinformation regarding whether the UE-B 100 b is a UE of a subscribercapable of using the network-assisted discovery service and informationregarding whether a specific service is in a state in which thenetwork-assisted discovery service is allowed for use.

The ProSe related information may be acquired from an HSS 540 or a ProSefunction server B 810 b by using the following methods.

First, when the ProSe related information is stored in subscriberinformation, the MME-B 510 b may acquire it from the HSS 540.

Second, when the UE-B 100 b is registered to the ProSe function server B810 b, or delivers the ProSe related information during a process ofregistering an application thereof, the MME-B 510 b may acquirecorresponding information from the ProSe function server B 810 b. Inthis case, information regarding whether the EPC-level ProSe discoverycan be used may be included in the ProSe related information.

Third, when the UE-B 100 b is registered to the ProSe function server B810 b, or delivers the ProSe related information during the process ofregistering the application thereof and when the ProSe function server B810 delivers the information of the HSS 540, the MME-B 510 b may acquirecorresponding information from the HSS 540.

(6) Then, the MME-B 510 b transmits a context request message to theSGSN-B 420 b in order to acquire a context for the UE-B 100 b.

(7) Upon receiving the context request message, the SGSN-B 420 btransmits a context response message including information regarding anISR capability thereof to the MME-B 510 b.

(8) The MME-B 510 b determines whether to activate the ISR.Specifically, the MME-B 510 b determines whether the conventional ISRactivation condition is satisfied, and at the same time, the MME-B 510 bconfirms whether the UE-B 100 b is in a state capable of performing theProSe related service or is scheduled to perform the service. Whetherthe conventional ISR activation condition is satisfied may be determinedaccording to whether both of the SGSN-B 420 b and the MME-B 510 b havethe ISR capability. In addition, whether the conventional ISR activationcondition is satisfied may be determined by additionally consideringwhether the SGSN-B 420 b has a context of the UE-B 100 b.

The confirmation regarding whether the UE-B 100 b is in the statecapable of performing the ProSe related service or is scheduled toperform the service may be performed by using the previously acquiredProSe capability information of the UE-B 100 b and enable stateinformation of the ProSe service. Herein, although the ProSe capabilityinformation of the UE-B 100 b may be acquired from the HSS, if the UE-B100 b has previously transmitted an attach request message to the MME-B510 b, it may be acquired from the attach request message. If the ProSecapability information is included in the attach request message, theMME-B 510 b may have transmitted an attach request accept message byinserting a ProSe authorized indicator in response to the attach requestmessage.

In addition, the confirmation may be performed by additionally using thepreviously acquired information regarding whether the EPC-level ProSediscovery can be used. The information regarding the EPC-level ProSediscovery may include information regarding whether the UE-B 100 b is aUE of a subscriber capable of using the network-assisted discoveryservice and information regarding whether a specific service is in astate in which the network-assisted discovery service is allowed foruse.

Further, in the confirmation, information regarding whether the MME-B510 b supports a ProSe service or a ProSe enabled UE may be additionallyused. In addition, in the confirmation, information which ispredetermined in the MME-B 510 b may also be used. The predeterminedinformation may be, for example, information instructing the ProSeenabled UE not to activate the ISR even if the MME-B 510 b has acapability of supporting the ISR.

According to the confirmation, if the UE-B 100 b is in the state capableof performing the ProSe related service or is scheduled to perform theservice, the MME-B 510 b may determine not to activate the ISR.

(9) The MME-B 510 b transmits a context ACK message to the SGSN-B 420 b.In this case, the context ACK message may set a value of an ISRAI flagshown in Table 6 below to 0.

(10) Subsequently, the MME-B 510 b transmits a TAU accept message inresponse to the TAU request message by inserting an indicator indicatingthat the ISR is not activated or an indicator indicating that the ISRshall be not activated.

(11) Since the ISR is not activated, the ProSe related procedure can beeffectively performed.

The TAU accept message includes information elements shown in Table 3below.

An information element ‘EPS update result’ of Table 3 is set to ‘100’indicating ‘TA updated and ISR activated’ when the ISR is activated,whereas when the MME-B 510 b determines not to activate the ISR asdescribed above, is set to 0000 indicating ‘TA updated’ as shown inTable 4.

TABLE 3 Information element (IE) Type Protocol discriminator Protocoldiscriminator Security header type Security header type Tracking areaupdate accept message identity Message type EPS update result EPS updateresult GUTI EPS mobile identity TAI list List for TAI (Tracking areaidentity) EPS bearer context status EPS bearer context status Locationarea identification Location area identification MS identity Mobileidentity EMM cause EMM cause T3402 value GPRS timer T3423 value GPRStimer Equivalent PLMNs PLMN list Emergency number list Emergency numberlist EPS network feature support EPS network feature support Additionalupdate result Additional update result

TABLE 4 Value (3 bits) of EPC update result 0 0 0 TA updated 0 0 1combined TA/LA updated 1 0 0 TA updated and ISR activated 1 0 1 combinedTA/LA updated and ISR activated

Not all of the procedures described up to now with reference to FIG. 12are necessarily performed, and only some steps thereof may be performedoptionally.

FIG. 13 is a flowchart illustrating a solution according to a secondexample of a first method.

A method shown in FIG. 13 is a method of exchanging mutually manipulatedinformation (i.e., even if an ISR capability is present, it ismanipulated as being not present) in order to prevent the ISR from beingactivated between network nodes. Detailed descriptions thereof are asfollows.

(1)˜(4) A UE-B 100 b selects an EUTRAN, and performs an attach procedurewith respect to an MME-B 510 b serving the UE-B 100 b. Specifically, theUE-B 100 b transmits an attach request message to the MME-B 510 b. ProSecapability information may be included in the attach request message.

(5) Thereafter, if the UE-B 100 b reselects a UTRAN, the UE-B 100 btransmits an RAU request message to the SGSN-B 420 b serving the UE-B100 b.

(6) Then, the SGSN-B 420 b transmits a context request message to theMME-B 510 b to acquire a context for the UE-B 100 b.

(7) Upon reception of the context request message, the MME-B 510 bdetermines how to insert ISR capability related information into acontext response message. Conventionally, if the MME-B 510 b has the ISRcapability, a flag ‘Idle mode Signalling Reduction Supported Indication’is set to 1 among indication flags in a context response message shownin Table 5 below. However, according to the first example of theaforementioned first method, even if the MME-B 510 b has the ISRcapability, whether to set the flag to 0 or 1 may be determined.

Whether to set the flag to 0 or 1 may be determined by using one or moreof the following information.

First, it may be determined by the MME-B 510 b on the basis ofinformation regarding whether the UE-B 100 b is in a state capable ofusing the EPC-level ProSe discovery. The information regarding theEPC-level ProSe discovery may include information regarding whether theUE-B 100 b is a UE of a subscriber capable of using the network-assisteddiscovery service and information regarding whether a specific serviceis in a state in which the network-assisted discovery service is allowedfor use.

Second, it may be determined by the MME-B 510 b on the basis ofinformation predetermined for a ProSe service/ProSe-enabled UE.

Third, it may be determined by the MME-B 510 b on the basis of ProSecapability information of the UE-B 100 b and enable state information ofa ProSe service.

(8) The MME-B 510 b transmits a context response message in which a flag‘Idle mode Signalling Reduction Supported Indication’ is set to 0 (i.e.,No ISR capability) to the SGSN-B 420 b according to the determination.

(9) The SGSN-B 420 b transmits a context ACK message to the MME-B 510 b.In this case, a value of an ISRAI flag shown in Table 6 below is set to0 in the context ACK message.

(10) In addition, the SGSN-B 420 b knows that the MME-B 510 b does nothave the ISR capability from the context ACK message, and thus transmitsto the UE-B 100 b an RAU accept message including an indicatorindicating that the ISR is not activated.

(11) As such, since the ISR is not activated, the ProSe relatedprocedure can be effectively performed.

TABLE 5 IE Description IMSI International Mobile Subscriber IdentityMME/SGSN UE MM It is included when a cause IE is set to a value Contextindicating “Request Accepted”. MME/SGSN UE EPS It is included when atleast one PDN connection for a PDN Connections UE exists. Sender F-TEIDfor It is included when the cause IE is set to the value Control Planeindicating “Request Accepted”. SGW node name Identifier of an S-GW usedby an old MME/SGSN. Indication Flags It is included when any one of thefollowing flags is set to 1. Idle mode Signalling Reduction SupportedIndication: It is included when the old MME/SGSN has ISR capability.ISRAU: It is set to 1 when the ISR is activated before the UE moves to anew SGSN/MME.

TABLE 6 IE Condition/Description Cause Indication It is included whenany one of the following flags flags is set to 1. SGWCI: An indicatorindicating that an SGW is changed, when a new S-GW is selected. ISRAI:It is set to 1 when an ISR is activated and an old SGSN/MME isinstructed to maintain a UE context.

(12)˜(18) On the other hand, when the UE-B 100 b reselects the EUTRANagain, a TAU procedure is performed with respect to the MME-B 100 b. Inthe TAU procedure, similarly to the previous RAU procedure, mutuallymanipulated information (i.e., even if an ISR capability is present, itis manipulated as being not present) is exchanged to prevent the ISRactivation.

As such, since the ISR is not activated, the ProSe related procedure canbe effectively performed.

Not all of the procedures described up to now with reference to FIG. 13are necessarily performed, and only some steps thereof may be performedoptionally.

Meanwhile, the second method described above in brief will be describedhereinafter.

FIG. 14 is a flowchart illustrating a solution according to a firstexample of a second method.

The second method is for deactivating a previously activated ISR for aproximity service as described above. It is described above that,according to the first example of the second method, a network node mayactively instruct a UE to deactivate the activated ISR. Further,according to a second example of the second method, each of networknodes may deactivate the ISR and thereafter may exchange informationthereon. According to the third example of the second method, it may bemutually requested to deactivate the ISR between the network nodes.

Hereinafter, the first example of the second method will be describedwith reference to FIG. 14.

(1) An MME-B 100 b serving a UE-B 100 b acquires the ProSe relatedinformation. As described above, the ProSe related information may beacquired from an HSS 540 or a ProSe function server B 810 b. Thedescription of FIG. 12 is applied herein.

(2) The MME-B 100 b determines whether an ISR is activated. If it isconfirmed that the ISR is activated but it is confirmed that a ProSerelated service can be performed or is scheduled to be performed on thebasis of the acquired ProSe related information, the MME-B 100 bdetermines whether to deactivate the ISR.

(3)˜(4) The MME-B 100 b deactivates the ISR activated for the MME-B 100b and thereafter requests an SGSN-B 420 b to deactivate the ISR.

(5) In addition, the MME-B 100 b requests the UE-B 100 b to deactivatethe ISR. In this case, in the conventional 3GPP, a mechanism by whichthe MME-B 100 b can request the UE-B 100 b to deactivate the ISR is notproposed. Therefore, according to one embodiment, in order to requestthe UE-B 100 b to deactivate the ISR, the MME-B 100 b may use a new NASmessage. Alternatively, when there is another NAS message to betransmitted to the UE-B 100 b, the MME-B 100 b sends it by inserting anindicator indicating ISR deactivation. Alternatively, the MME-B 100 bmay transmit a TAU accept message/RAU accept message by inserting theindicator indicating the ISR deactivation only after the UE-B 100 bperforms TAU/RAU.

Upon receiving the ISR deactivation request, the UE-B 100 b locallydeactivates the ISR.

(6) As described above, the ISR deactivation is requested to the SGSN-B420 b and the UE-B 100 b, and thereafter the MME-B 100 b reports to theHSS 540 or the ProSe function server B 810 b that the ISR is deactivatedand thus a state is updated. This may be performed through an ISR statusindication shown in Table 7 below.

(7) As such, since the ISR is deactivated, the ProSe related procedurecan be effectively performed.

TABLE 7 IE Condition/Description Action This IE shall include one of theapplicable Values: Indication Deactivation Indication: If this is set to1, it indicates that an ISR is deactivated. Paging Indication: If thisis set to 2, it indicates that a paging signal is transmitted to a UE inan idle state.

Not all of the procedures described up to now with reference to FIG. 14are necessarily performed, and only some steps thereof may be performedoptionally.

The content described up to now can be implemented in hardware. Thiswill be described with reference to FIG. 15.

FIG. 15 is a block diagram of an SGSN 420 and an MME 510 according to adisclosure of the present specification.

As shown in FIG. 15, the SGSN 420 includes a storage unit 421, acontroller 422, and a transceiver 423. Further, the MME 510 includes astorage unit 511, a controller 512, and a transceiver 513.

The storage units 421 and 511 store the aforementioned method.

The controllers 422 and 512 control the storage units 421 and 511 andthe transceivers 423 and 513. More specifically, the controllers 422 and512 respectively execute the methods stored in the storage units 421 and511. Further, the controllers 422 and 512 transmit the aforementionedsignals via the transceivers 423 and 513.

Although exemplary embodiments of the present invention have beendescribed above, the scope of the present invention is not limited tothe specific embodiments and the present invention may be modified,changed, or improved in various ways within the scope of the presentinvention and the category of the claims.

What is claimed is:
 1. A method of determining whether to activate anidle mode signaling reduction (ISR) capability in a network entity formanaging mobility of a user equipment (UE), the method comprising:obtaining information related to a proximity service of the UE;receiving from the UE a location update request message; determiningwhether to activate the ISR on the basis of ISR capability informationof a network node by which the UE has been served just previously, ISRcapability information of the network entity, and information related tothe proximity service of the UE; and transmitting a location updateaccept message to the UE after the determination, wherein thedetermining comprises one or more of: confirming whether both of thenetwork entity and the network node have an ISR capability on the basisof the ISR capability information of the network node and the ISRcapability information of the network entity; confirming whether the UEis scheduled to perform the proximity service; and confirming whether anetwork-assisted discovery is scheduled to be performed, wherein duringthe determining, even if it is confirmed that both of the network entityand the network node have the ISR capability, the ISR is determined tobe deactivated when it is confirmed that the UE is scheduled to performthe proximity service and the network-assisted discovery is scheduled tobe performed.
 2. The method of claim 1, wherein the location updaterequest message is a tracking area update (TAU) request message or arouting area update (RAU) request message.
 3. The method of claim 1,wherein the information related to the proximity service of the UEcomprises one or more of: capability information for the proximityservice of the UE; proximity service enable state information of the UE;information regarding whether the UE is in a state capable of performingthe proximity service or is scheduled to perform the proximity service;and information regarding a network-assisted discovery.
 4. The method ofclaim 3, wherein if the information related to the proximity service ofthe UE comprises the information regarding the network-assisteddiscovery, the information regarding the network-assisted discoverycomprises one or more of: information regarding whether the UE is a UEof a subscriber capable of using the network-assisted discovery service;and information regarding whether a specific service is in a state inwhich the network-assisted discovery service is allowed for use.
 5. Themethod of claim 1, further comprising: upon receiving the locationupdate request message, transmitting a request message for a context ofthe UE to a network by which the UE has been served just previously; andreceiving a context response message from the network node, wherein thecontext response message comprises information regarding an ISRcapability of the network node.
 6. The method of claim 1, wherein if thedetermination result shows that the ISR is not activated, the locationupdate accept message comprises an update result indicating that only alocation update is performed.
 7. The method of claim 1, wherein thenetwork entity is a mobile management entity (MME), and the network nodeby which the UE has been served just previously is a serving generalpacket radio service support node (SGSN).
 8. A method of determiningwhether to activate an idle mode signaling reduction (ISR) capability ina network entity for managing mobility of a user equipment (UE), themethod comprising: receiving by the network entity a context requestmessage from a network node for newly serving the UE; determiningwhether there is an ISR capability to be included in a context responsemessage in response to the context request message on the basis ofinformation related to the proximity service of the UE; and transmittingto the network node the context response message generated depending onthe determination, wherein the information related to the proximityservice of the UE comprises one or more of: capability informationregarding the proximity service of the UE; proximity service enablestate information of the UE; information regarding whether the UE is ina state capable performing the proximity service or is scheduled toperform the proximity service; and information regarding anetwork-assisted discovery, wherein during the determining of whetherthere is the ISR capability, if it is confirmed that the UE is scheduledto perform the proximity service and the network-assisted discovery isscheduled to be performed, even if the network entity supports the ISRcapability, the context response message is configured not to supportthe ISR capability.
 9. The method of claim 8, wherein if the informationrelated to the proximity service of the UE comprises the informationregarding the network-assisted discovery, the information regarding thenetwork-assisted discovery comprises one or more of: informationregarding whether the UE is a UE of a subscriber capable of using thenetwork-assisted discovery service; and information regarding whether aspecific service is in a state in which the network-assisted discoveryservice is allowed for use.
 10. The method of claim 8, wherein if thenetwork entity is a mobility management entity (MME), the network nodeis a serving general packet radio service support node (SGSN), and ifthe network entity is the SGSN, the network node is the MME.